Overview

Comprehensive Description

Biology/Natural History: Spawns late spring and summer. In Washington spawning is simultaneous (the same day) along several kilometers of beach, triggered by a sudden rise in water temperature to about 13C (usually in late May or June). Intensity of spawning varies dramatically from year to year. In Alaska they spawn every year, but not simultaneously, in July and August. Larvae are pelagic for about 8 weeks. Live about 12 years in Washington. This species is frequently dug by humans for food, but as with most species on the open coast, is susceptible to paralytic shellfish poisoning (PSP, toxic to humans) due to ingesting too many dinoflagellates such as Gonyaulax during the summer. The animal typically remains just below the surface, with a dimple in the sand above the siphon. When disturbed, for example by human footsteps approaching, it begins digging rapidly. Predators include flatfish such as the starry flounder and the Dungeness crab Cancer magister. May have a commensal nemertean worm, Malacobdella grossa, or the pea crab Pinnixia faba in its mantle cavity.

These clams are called razor clams for a reason. If while a clam digger grasps the ventral side of the shell in the rush to catch up with the rapidly-digging clam, he may pay for it with a deeply cut hand. Fortunately, the clams always orient with the hinge toward the ocean so if a digger will always reach into the hole on the oceanward side he will be safe from cuts (but will still have to dig fast!)

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As with all members of family Cultellidae, this large clam species is more than twice as long as it is wide, has a true hinge plate, 2 adductor muscle scars of similar size, and a shiny brown or olive periostracum. They are not more than 3x as long as high, and the dorsal margin is not concave. Siliqua patula is a large clam (grows much larger than 5 cm), olive-green or olive-brown with perhaps some purple near the umbones, and the internal supporting rib diverges from the dorsoventral axis by about 30 degrees (photo). Shell, up to 17 cm long and rounded at the ends, is thin and cracks easily. In a live animal the valves gape everywhere but at the hinge, and the siphons are fused (photo). The shell interior is white with pinkish tint (photo).

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Physical Description

Look Alikes

How to Distinguish from Similar Species: The other related species in this area are less than 5 cm, subtidal, and with alternating colored bands on the shell. The jackknife clams (genus Tagelusand Solen) are also smaller and much more elongated.

This species has an elongated oblong narrow shell, which ranges from 3 to 6 inches (8 to 15 cm) in length in the southern portion of its range, with individuals up to 11 inches (28 cm) found in Alaska.[1] It is similar to the smaller Atlantic razor clam, Siliqua costata, which is found on the East Coast of the United States. Another eastern species in the same family is sometimes also called a razor clam: Ensis directus, but this is in a different genus, is not very similar, and is also known as the Atlantic jackknife clam.

Pacific razor clams are highly desirable and edible, collected both commercially and by recreational harvesters.[2] Razor clams, like other shellfish, may sometimes accumulate dangerous levels of domoic acid, a marine toxin.[3] Harvesters should be sure to check current public health recommendations before collecting razor clams. Razor clams are commonly battered and fried in butter, or made into a clam chowder.

Razor Clam harvesting is typically authorized by state officials several times a year.[4] Harvesters locate the clam by looking for a "show," which can present as either a hole or depression in the sand.[5] Some razors expose their necks while the surf has receded, making them far easier to spot; some locals refer to these colloquially as Pollom Clams. [6]